Influence of Landau-level mixing on Wigner crystallization in graphene

Graphene, with its massless linearly-dispersing carriers, in the quantum Hall regime provides an instructive comparison with conventional two-dimensional (2D) systems in which carriers have a nonzero band mass and quadratic dispersion. We investigate the influence of Landau level mixing in graphene on Wigner crystal states in the $n^\mathrm{th}$ Landau level obtained using single Landau level approximation. We show that the Landau level mixing does not qualitatively change the phase diagram as a function of partial filling factor $\nu$ in the $n^\mathrm{th}$ level. We find that the inter-Landau level mixing, quantified by relative occupations of the two Landau levels, $\rho_{n+1}/\rho_{n}$, oscillates around 2% and, in general, remains small ($< 4$) irrespective of the Landau level index $n$. Our results show that the single Landau level approximation is applicable in high Landau levels, even though the energy gap between the adjacent Landau levels vanishes.